#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
    float x1,x2=1,a;
    scanf("%f",&a);
    do
    {
        x1=x2;
        x2=(x1+a/x1)/2;
    }
    while(fabs(x1-x2)>1E-5);
    printf("%.4f\n",x2);
    return 0;
}
